Patent Document 1 discloses a technology for estimating a road surface shape based on the behavior or actions of a forerunning vehicle (vehicle-in-front) running in front of a driver's own vehicle. More specifically, in Patent Document 1, the behavior of the vehicle-in-front is detected based on the behavior of mirrors or the license plate of the vehicle-in-front, and then the type or model of the vehicle-in-front is selected based on its amplitude and its convergence time. After the vehicle type has been selected, the road surface shape is estimated based on the selected vehicle type and the behavior of the vehicle-in-front. The thus estimated road surface shape is used to perform preview control of an active suspension apparatus, for instance.